Employers decided which insurance company to work with. Their motivation is clear, to save money. As a secondary objective, they want happy employees. However, the insurance company is selling insurance to your employer, not you. So they craft policies that are lucrative to your employer. Maybe 60% of employees are happy with what they get, but the other 40% are pretty much hosed. If they want a different insurance company they need to pay full price and the employer is not allowed to compensate the employee on what their portion might have been. End result: consumers do not choose their insurance company, their employer does. If they want to change their insurance, they can't until the next benefit choice period dictated by the IRS.
Now you, Joe Consumer, want to go to the doctor. You take your handy dandy provider directory (or go online) and you select from the list of doctors your HMO allows you to go see. You may know you need an orthopedic doctor to deal with your knee problems but that's too bad, you need to go to a primary care physician first (and pay for that useless appointment that you don't need). This primary care physician's job is to limit the amount of advanced care patients receive. In fact, in some cases, primary care physicians get a bonus based on how few referrals they give.
Let's say you do get a referral. Then you go to where the HMO tells you to go to with even more limited choices in the provider directory. Let's change the scenario, let's say instead of knee problems you have cancer. You hear good things about the Mayo Clinic and you want to get care there. Too bad, you need to go where your HMO tells you to go to. You may have a better shot at survival at Mayo, it doesn't matter.
You may wish to explore alternative treatments, however, your doctor who knows what your insurance company will and will not pay for better than you ever will, simply will limit you to those choices which your insurance company has already decided you will have. He knows that they won't pay (and he probably won't get paid) if his plan of care deviates from the dictates of the insurance company's accountants. These people have never seen you, have no information about you but have near complete control over your health care decisions based on some sparse paperwork sent back and forth. The patient will never get the opportunity to talk to much less negotiate with these people.